1. Field of the Invention
The present invention relates to an image sensor that includes a plurality of imaging pixels and a plurality of pupil division-type focus detection pixels arrayed on a single substrate, an image sensor as a photoelectric conversion element, an imaging device equipped with the image sensor and the imaging method.
2. Description of the Related Art
There is an imaging device known in the related art equipped with an image sensor having imaging pixels and pupil division-type focus detection pixels disposed together on a single substrate, which captures an image formed on the image sensor and also detects the focus adjustment state of the image (see Japanese Laid Open Patent Publication No. H01-216306).
The following problems arise in the imaging device in the related art described above, which detects the focus adjustment state based upon the image shift amount between a pair of images detected through the pupil division-type method. Namely, in order to assure highly accurate detection of the focus adjustment state in the range around the image focus match position, the focus detection pixels should be disposed densely so as to set a short (fine) image detection pitch. At the same time, the focus detection pixels should be arrayed over a long range to enable detection of a large image shift amount between the pair of images when the image is greatly defocused from the focus match position (hereafter may also be referred to as large defocusing) by assuring a sufficient image shift amount margin. In short, the focus detection pixels should be disposed densely over a long row in order to assure both highly accurate focus detection and detection of a large defocus amount.
For the image sensor to provide high quality image signals, pixel signals at the focus detection pixel positions should be interpolated based upon the signals from the surrounding imaging pixels. This means that the likelihood of a significant interpolation error is bound to be high when interpolating (correcting) pixel signals at positions taken up by the individual focus detection pixels, which are disposed densely over a long range, based upon the signals from the surrounding imaging pixels.